Studies on the utilization of synthetic soil conditioners to horticulture. (II)

The effect on the physical properties of the potted soils

Abstract

The effect of application of some synthetic soil conditioners, such as A-22, Aerotil (both HPAN) and Krilium-6 (VAMA), on the physical proper-ties of potted soils was studied. Each conditioner was applied at the rate of 0.06 per cent by wei-ght to soil. The soil used was Anzyo clay loam, containing 3.5 per cent humus, 37.5 per cent clay, 13.6 per cent silt, 20.0 per cent fine sand, 26.9 per cent coarse sand, and 56.4 per cent ini-tial soil aggregates. To the contrast, six plots, i.e. untreated, rotted organic matter added, compost, river-sand added, moss mulched and straw mulched, were also used. Each soil was potted, and then weathered at the open field. When the soil dried, the same volume of water was given to each pot. The physical properties of each soil were determined first at the beginning of the experiment (three days after the treatment) and then three or four months after.
Appilication of these soil conditioners, without exception, remarkably improved soil structure and especially increased the percentage of watersta-ble aggregates larger than 0.5mm. They also in-creased the aeration porosity, infiltration and percolation rates, but reduced the rate of evaporation from the soil surface. Moreover, the compactibili-ty of the soils and the formation of surface crust in the potted soils were prevented by the treat-ment with the soil conditioners. These physical conditions in the treated soils were satisfactory for pot-soil as well as those of compost-soil. Consequently, it is conceivable that application of the synthetic soil-conditioning polyelectrolytes to the pot-soil or to the bed-soil in greenhouse are very effective. It was found, however, that the effectiveness of the application of the chemicals only to soil surface was not persisted through long period, because of the aggregate destruction by the beating action of rain-drops. The field water capacity, the moisture equivalent and the avail-able water capacity in the soil were unchanged or slightly decreased by the treatmeht. But, the application of the soil conditioners' may indirectly increase the available water in soil by aiding the infiltration but preventing the evaporation.